1. Field of the Invention
The present invention relates to a parking assist apparatus configured to estimate a reflection-point position on an object, at which a detection wave emitted from a distance sensor mounted in a self-vehicle is reflected, to thereby estimate parking-space information of the self-vehicle so as to provide parking assistance based on the result of estimation.
2. Description of the Related Art
Hitherto, there has been proposed a parking assist apparatus configured to provide appropriate parking assistance to a driver who attempts to park a self-vehicle in a parking space between two parked vehicles (for example, see Japanese Patent No. 5506803 and Japanese Patent Application Laid-open No. 2013-220745).
In the related art disclosed in Japanese Patent No. 5506803, distance data corresponding to a corner portion of each of the parked vehicles is extracted from a time series of distance data from the self-vehicle to each of the parked vehicles, which is measured by using distance sensors mounted in the self-vehicle. The extracted distance data is subjected to noise-component removal and data interpolation using curve approximation as data processing.
Subsequently, a reflection-point position on each of the parked vehicles is estimated from the distance data that is subjected to the data processing and sensor-position data indicating a movement locus of a sensor position of the distance sensor. Further, a width of the parking space is estimated based on a corner position of each of the parked vehicles, which is obtained from the estimated reflection-point positions, thereby determining whether or not the self-vehicle can be parked in the parking space.
In the related art disclosed in Japanese Patent Application Laid-open No. 2013-220745, after the corner position of each of the parked vehicles is detected from the distance data from the self-vehicle to each of the parked vehicles, which is measured by using the distance sensors mounted in the self-vehicle, and the sensor-position data indicating the movement locus of each of the distance sensors, a supposed side-surface range is set.
Subsequently, the supposed side-surface range is divided into a near-side supposed side-surface range and a far-side supposed side-surface range. The corner positions are corrected by using the reflection-point positions present in the near-side supposed side-surface range, while the reflection-point positions present in the far-side supposed side-surface range are linearly approximated. In this manner, the side surfaces of the parked vehicles are estimated.
However, the related art has the following problems.
According to the related art disclosed in Japanese Patent No. 5506803, the corner positions of the parked vehicles are estimated while the self-vehicle is moving past a side of the parking space so as to determine whether or not the self-vehicle can be parked in the parking space. When it is determined that the self-vehicle can be parked in the parking space, the self-vehicle is guided into the parking space.
In this case, the parking space is estimated as, for example, a rectangle having a line segment connecting the corner positions as one side and a self-vehicle width in a case of parallel parking and a self-vehicle length in a case of perpendicular parking as a length of another side. In general, however, a vehicle width of the parked vehicle, a vehicle length of the parked vehicle, and a parking direction such as an inclination of the parked vehicle differ for each of the parked vehicles. Further, a shape of the estimated parking space is different from that of an actual parking space.
Therefore, there is a problem in that the self-vehicle cannot be appropriately guided into the parking space between the parked vehicles merely by estimating the corner positions of the parked vehicles as in the related art disclosed in Japanese Patent No. 5506803.
According to the related art disclosed in Japanese Patent Application Laid-open No. 2013-220745, the reflection-point position on each of the parked vehicles is estimated even when the self-vehicle is guided into the parking space, while the supposed side-surface ranges are set so as to correct the parking space that is estimated based only on the corner positions.
In this case, the supposed side-surface range is set as a rectangle having certain width and depth in a direction orthogonal to a straight line that is obtained by connecting the corner positions of the parked vehicles, which are estimated while the self-vehicle moves past the side of the parking space.
However, accuracy of estimation of the corner positions depends on a model of the parked vehicle. For example, the accuracy of estimation of the corner positions for a parked vehicle having an angular shape differs from that for a parked vehicle having a round shape. Further, a model of an actually parked vehicle cannot be known.
Therefore, the related art disclosed in Japanese Patent Application Laid-open No. 2013-220745 has the following problem. Specifically, when the accuracy of estimation of the corner positions is low, the side surfaces of the actually parked vehicles are not contained in the supposed side-surface ranges. Thus, the self-vehicle cannot be appropriately guided into the parking space between the parked vehicles.